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The Health of the Oceans in a Single Number

How are the oceans faring? Are they getting better or worse? And how should governments respond? These are thorny questions; people value different things about the ocean—such as sushi or protecting bluefin tuna—that sometimes are in conflict.

Now researchers have completed the most comprehensive effort ever to provide an overview of the state of the seas. They hope the new Ocean Health Index will raise awareness of the connections between humans and the oceans, highlight trade-offs in how people use marine resources, and point to areas where more data are needed. "It's a heroic effort," says fisheries biologist Steven Murawski of the University of South Florida, St. Petersburg.

The bottom line score for the oceans: 60 out of 100. "There are a lot of things to celebrate," says lead author Benjamin Halpern of the University of California, Santa Barbara (UCSB), but also "a lot of room for improvement." The team also presents scores for individual countries and hopes they will help in policymaking.

"It really is a useful and important tool for starting a discussion on management of the oceans," says oceanographer Katherine Richardson of the University of Copenhagen, who was not involved. She calls the index "a huge step forward." Unlike previous global measures of the ocean, which tend to focus on nature, the new index incorporates a broad range of societal values.

The results, published online today in Nature, come from a joint effort. One group of scientists working at UCSB’s National Center for Ecological Analysis and Synthesis had been searching for indicators of human interactions with the ocean. Meanwhile, philanthropist William “Beau” Wrigley was funding several organizations, including Conservation International and the New England Aquarium, to create an Ocean Health Index. They teamed up, and over the past several years more than 40 scientists have worked on the $5.2 million project.

To start, the two groups came up with a top 10 list of things that people tend to value about the oceans. Many are obvious choices, such as food, biodiversity, and clean water. Others may be less familiar to the developed world, such as the ability to sustain artisanal fisheries, which account for half of the world's catch and are often the key to subsistence diets. "In a lot of countries, [artisanal fishing] is a fundamental way that people interact with the oceans," Halpern says.

Measuring how nations were doing in reaching those 10 goals was no easy task. Sometimes the group was constrained by a paucity of data. (The high seas aren't included at all.) For some of the goals, they needed to be creative: To measure the value of tourism and recreation, for example, they used international flights as a proxy, which underestimates domestic tourism. Even though better data exists for some countries, international travel was the only dataset available for all countries.

In other cases, quantification was the difficult task. Take the vague-sounding "sense of place." This reflects cultural values, but how do you put a number on that? The team chose two dimensions: the degree of preservation of iconic species, such as penguins or polar bears, and of beautiful beaches or other "lasting special places." In lieu of any other comprehensive data, the group relied on the fraction of coastal area under protection.

For each of the 10 metrics, the team then defined what it would take to earn a top score of 100. The top score for fisheries was determined by looking at how close nations were to achieving a well-studied level of harvest called maximum sustainable yield. Most goals aren't defined by pristine conditions or resemblance to a long-ago state untouched by humans. Rather, the goals are "ambitious, yet achievable, conditions in a healthy ocean," as the team wrote in a background article. The scores depend not only on current conditions, but also on the direction toward or away from sustainability. "It's focusing us on the trends," says Margaret Caldwell, a lawyer at Stanford University who directs the Center for Ocean Solutions, and who was not involved. "That is really important."

To come up with its rankings, the team weighted each of the 10 scores equally. Countries ranged from 36 (Sierra Leone) to 86 (Jarvis Island, an uninhabited island U.S. territories in the South Pacific). As expected, developed countries tended to score higher because they have more resources for protection, can import seafood, and often harmed or destroyed marine resources long ago—whereas developing countries are penalized for currently inflicting damage.

The group is now developing a software tool that will allow users to add their own data and to calculate scores. As an example, the researchers came up with four alternate weighting schemes to show how policymakers could evaluate whether their country is headed in the direction they want, whether for strong conservation or high extraction of marine resources. Richardson says the scores might provide useful peer pressure to improve commitments to intergovernmental agreements. "If you have a low index,” she says, “you'll be embarrassed when you come onto the political scene."